Hydraulic wheel drawbar



May 28, 1963 w. v. LOHRMAN ETAL 3,091,296

HYDRAULIC WHEEL DRAWBAR Original Filed Jan. 26, 1959 5 Sheets-Sheet 1INVENTORS.

WILLIAM v. LOHRMAN WILLIAM E. KNAPP 4 1%; 8 B (6 g ATTORNEY May 28, 1963w. v. LOHRMAN ETAL 3,091,296

HYDRAULIC WHEEL DRAWBAR Original Filed Jan. 26, 1959 5 Sheets-Sheet 2 I5INVENTORS.

WILLIAM v. LOHRMAN y WILLIAM E.KNAPP B TORNEY M y 8, 1963 w. v. LOHRMANETAL 3,091,296

HYDRAULIC WHEEL DRAWBAR 5 Sheets-Sheet 3 Original Filed Jan. 26, 1959INVENTORS WILLIAM V. LOHRMAN WILLIAM E. KNAPP BY A ORNEY May 28, 1963 w.v. LOHRMAN ETAL 3,091,296

HYDRAULIC WHEEL DRAWBAR Original Filed Jan. 26, 1959 5 Sheets-Sheet 4INVENTORS. WILLIAM V. LOHRMAN WILLIAM E. KNAPP ATTORNEY May 28, 1963 w.v. LOHRMAN ETAL 3,091,296

HYDRAULIC WHEEL DRAWBAR Original Filed Jan. 26, 1959 5 Sheets-Sheet 5INVENTORS. WILLIAM V. LOHRMAN WILLIAM E. KNAPP This application is adivision of our copending application Ser. No. 788,827, filed January26, 1959, now Patent No. 2,995,385, granted August 8, 1961, forHydraulic Wheel Drawbar.

This invention relates gene-rally to agricultural implements and moreparticularly to wheeled folding drawbar supports of the type to which aplurality of units, such as spike tooth harrow sections, for example,may be connected in side-by-side relation to provide an implement thatworks a relatively wide strip of ground.

The object of and general nature of this invention is the provision ofan agricultural implement of the abovedescribed type having new andimproved power operated drawbar rocking means. Further, it is animportant feature of this invention to provide a new and improvedagricultural implement incorporating a foldable drawbar on a wheeledcarrier frame combined with a power operated actuator to lift theimplement for transport.

More specifically, it is a feature of this invention to provide a poweroperated actuator having means utilizing a first full stroke of a ram orpower cylinder to raise the drawbar and associated implement unitsthrough approximately 4-5 and a second full stroke to raise the drawbarand implements a second 45 to their completely raised position.

These and other objects and advantages of this invention will beapparent to those skilled in the art after a consideration of thefollowing detailed description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a fragmentary perspective view showing a wheel carriedhydraulic drawbar support in its working position in which the outerbars are arranged in their wide spread or laterally outwardly extendingrelation with the outer end of the outer bars supported on a pair ofground wheels. 7

FIG. 2 is an enlarged perspective view of one of the supporting wheelsand its mounting structure connected with the outer end of theassociated outer bar, the parts being shown in the positions they occupywhen arranged for operation as illustrated in FIG. 1.

FIG. 3 is a perspective view showing the field transport position of thedrawbar, the outer bars and the associated wheels being shifted byhydraulic power through approximately 45 from the position shown in FIG.1 so as to raise the associated harrow sections entirely off the ground.

FIG. 4 is a view similar to FIG. 2 showing the outer wheel turned andshifted into a position parallel with the associated support bar butwhile the latter is still supported on an associated stand. FIG. 5 is aview similar to FIG. 3 showing the harrow sections raised throughsubstantially 90, with the outer ends of the outer bars supported on theouter ground wheels so that when the operator drives forward the outerbars will be swung pivotally into a trailing or narrow transportposition.

FIG. 6 is a fragmentary view of a hydraulic lifting unit, showing thesame in the position it occupies when holding the Working implementunits in their field transport position.

FIG. 7 is a fragmentary perspective view of the wheel supported drawbarof this invention when disposed in its States PatentO 3,091,296 PatentedMay 28, 1963 road or transport position, portions being omitted forpurposes of clarity.

FIG. 8 is an enlarged fragmentary view of one of the adjustable groundwheels arranged in its position extending at a slight angle to theassociated outer bar so that, when the outfit backed in its roadtransport position (FIG. 7), the angle of the ground wheels will causethe outer bars to be swung laterally outwardly until they are disposedin alignment with the center bars in their widespread position, similarto that of FIG. 1.

Referring first to FIG. '1, the principles of this invention have beenillustrated as incorporated in a wheel supported folding drawbararrangement particularly adapted to carry five spring tooth hai-rowsections, each indicated by the reference numeral 10, the harrowsections 10 being conventional so far as the principles of thisinvention are concerned. The folding drawbar arrangement shown in FIG. 1incorporates a wheeled carriage 11 that includes a pair of laterallyspaced apart forwardly converging frame members 12, the front end ofwhich are provided with hitch means 13 to which a tractor, representedby the tractor drawbar 14 (FIGS. 3 and 7), may be connected in the usualway. The carriage 11 is supported on spaced apart wheels 15 and fromFIG. 1 it will be seen that frame members 12 extend rearwardly beyondthe wheels 15 and carry vertically extending apertured lug-s 16 to whicha rockable central transversely disposed bar 17 is connected, as bypairs of apertured lugs 18, with a pivot pin 19 hingedly connecting eachpair of lugs 18 with the associated apertured frame section '16. Thewheel axle 55 (FIG. 7) carrying the wheels 15 is fixed to the framemember-s 12 by any suitable means. When the front end of the carriage 11is hitched to the tractor 14, the carriage is supported at its rearportion on the wheels 15 and at its forward portion on the tractor,thereby providing a stable arrangement.

The tractor 14 (FIG. 3) is equipped with the usual hydraulic poweroperated lift mechanism and includes a remote ram unit 20 connected intothe tractor hydraulic system by a pair of hose lines 21. For purposes ofclarity, the unit 20 has been omitted in FIG. 1. The mounting of theunit 20 and associated connections, which form an important part of thisinvention, will be described in detail below, and therefore it willsutfice for the present to note at this point that by utilizing the unit20, the center drawbar section 17 may be rocked about a transverse axis,as defined by the pins 19, from a working or lowered position, shown inFIG. 1, through substantially 45 so as to lift the associated implementunits .10 otf the ground (FIG. 3) and then through another 45 to raisethe units 10 into a substantially vertical position as indicatedfragmentarily in FIG. 5.

The outer drawbar members are indicated at 25 in FIG. 1 and in theirworking positions these members extend axially outwardly and insubstantial alignment with the center power-operated drawbar member 17,the outer bars 25 being connected with the center bar 17 throughuniversal joint connections indicated at 26, such articulated jointmeans being conventional so far as this invention is concerned. In theworking or laterally outwardly extended position, the outer portions ofthe outer bars 25 are reinforced by braces in the form of truss bars 28.As best shown in FIG. 2, the outer end of each truss bar 28 is providedwith an attaching plate 31 that is apertures to receive a quickdetachable pin 32 connecting the part 31 with a pair of apertured lugs33 that are fixed to the adjacent portion of the associated outer bar25. The inner end (FIG. 3) of each truss bar 28 is apertured to receivea quick detachable pin 35 that connects the bar to an apertured lug 36carried by the adjacent frame member 12. A plurality of openings 37 ineach lug 36 provide for optional connection of the truss bars 28 to thecarriage 11 so as to provide some adjustment for the outer bars in theirextended or working position. The center bar 17 and the outer bars 25carry intermediate supporting arms 41, each member 41 comprising anangle bent into suitable formation and apertured to receive clampingU-bolts 42. Each set of arms 41 is fixed to the associated bar indifferent positions of adjustment along the bar, depending upon the sizeand character of implement units connected therewith. Preferably, asShOvWIl in FIG. 1, the rear ends of the bars 41 are provided withsupporting chains 44 that extend from the bars generally to the centralportions of the associated units whereby when the drawbar members 17 and25 are raised, as by operation of the power unit 20, the implement units10 are raised, as to the position shown in FIG. 3 or to the positionshown in FIG. 5. Draft is applied to the implement units, such as theharrow sections 10 shown in FIG. 1, by pairs of pull chains 47connectible with the forward portions of the associated implement units10 and with hitch brackets 48 clamped to the associated bars 17 and 25by the associated clamping bolts 42.

The articulated drawbar means '17, 25 is adapted to be rocked from anormal working position, FIG. 1, through approximately 45 to a fieldtransport position, FIG. 3, in which the several implement units 10 arelifted off the ground. However, in this field transport position theouter bars 25 and the associated implement units are still in their widespread position, but the implement may readily be turned or maneuvered,provided there is sufiicient space to do so. Also, the implement may, ifdesired, and if there is adequate space, be transported in this positionfrom place to place, but in View of the extra width of the implementwhen arranged in this way, which may be undesirable where maneuvering inrelatively confined space is required, provision is made foradditionally rocking the drawbar means 17, 25 through another 45 so asto raise the arms 41 substantially to a vertical position as shown inFIG. 5. The wheeled drawbar may now be narrowed for transport throughgates, along roads and lanes, etc., by the following steps. First, thetruss bars 28 (FIG. 1) are disconnected, after which the outer bars 25may swing about one of their universal joint axes rearwardly into afolded or transport position, as by driving the implement forwardly ashort distance from the position shown in FIG. 5. The universal joints26 are so arranged that when the section 17 is rocked through 90 by theoperation of the power unit 20, the universal joint pivots 26a aresubstantially vertical, which permits the outer bars 25 to swinghorizontal ly rearwardly from the position shown in FIG. to the positionshown in FIG. 7.

According to this invention, new and improved means have been providedfor mounting the tractor power cylinder 20 on the carriage 11 so as toutilize the full capacity of the unit 20 for raising the implements toeach of the two stages mentioned above. The cylinder mounting means willnow be described.

The apertured lugs 36 (FIG. 3) mentioned above form a part of atransverse bar 50 that is securely fixed, as by bolts or the like, tothe lower flanges of the forward portions of the frame members 12. Thelatter members are in the form of channels having their upper and lowerflanges extending laterally inwardly, and the lower flanges areapertured to receive the above mentioned bar-attaching bolts. A pair ofelongated vertical plates 52 and 53 are fixed at the forward ends to thegeneral central portion of the transverse bar 50 and the rear ends ofthe plates 52 and 53 are fixed to the generally central portion of theaxle 55 which may take the form of a transverse pipe member, on whichthe wheels 15 are journaled. The two plates 52 and 53 are fixed to thecarriage with a space between the plates so as to provide for thereception of the cylinder-supporting arms therebetween. One of thecylinder-supporting arms is indicated at 56 (FIG. 3) and is mounted forpivotal movement at its lower end on a transverse pivot 58. The upperend of the arm 56 extends beyond the plates 52 and 53 and the upperportion is apertured to receive a pivot member 59 that connects theforward or piston end 60 of the unit 20 to the arm 56. Below the pivot59 the arm 56 is apertured to receive a cross pin 61 to which a pair oflift bars 62 are pivotal-1y connected. The bars 62 extend divergentlyrearwardly to receive a transverse reinforcing crosspiece 63 and therear ends of the bars 62 are provided with bifurcated portions 64 '(FIG.5) that are apertured to receive pivot pins 65 by which the bars 62 areconnected to arms 67 that are welded 'to the end portions of the centerdrawbar member 17. Thus, rocking the forward arm or lever 56 serves torock the drawbar 17 and the associated end bars 25 for raising andlowering the associated implement units 10. The optionally operablemeans that is provided for holding the arm 56 in different positions, asnecessary to provide the two-stage operation mentioned above, will bedescribed below.

The rear portions of the plate members 52 and 53 are apertured toreceive a pin 71 (FIG. 3) on which the lower apertured end of the rearcylinder-receiving arm 72 is mounted. The arm 72 is apertured at itsuppermost end to receive a quick attachable pin 73 that attaches therear or cylinder end of the unit 20 to the arm 72. A rear stop 75 iswelded in between plates 52 and 53 and is disposed in a position tolimit the rearward swinging of the arm 72 when the parts are raised asshown in FIG. 3, the stop 75 serving as an abutment against which theunit 20 may operate to shift the forward arm 56 from the position shownin FIG. 1 to the position shown in FIG. 3, which movement of the arm 56and links 62 serves to rock the drawbar 17, 25 through approximately 45and thus raises the implement units 10 off the ground. In moving the arm56 to the position just mentioned, the unit 20 has extended its fullpredetermined amount, and this is sufficient to shift the arm 56 aslight distance forwardly of a pair of openings 77 (FIG. 3) in theforward portions of the plates 52 and 53. A pin 78 may now be disposedin the openings 77 after which retraction of the unit 20 acts againstthe pin 78 as an abutment to swing the rear arm 72 forwardly tosubstantially the position shown in FIG. 6, this being an idle movementso far as raising or lowering the implement units 10 is concerned. Theaforesaid forward movement of the rear arm 72 carries the latter into aposition substantially in contact with an abutment or stop 79 that isfixed to the plates 52 and 53 a distance forward of the rear stop 75.The movement on the arm 72 up against the stop 79 disposes the arm 72 ina position slightly ahead of a pair of openings 81 formed in the plates52 and 53 so that a pin, such as pin 82 shown in FIG. 5, may now bedisposed in the openings 81 to serve as an abutment preventing therearward movement of the arm 72. Extension of the power unit 20, whenthe pin 82 is in place as shown in FIG. 5, results in an additionalforward swinging of the arm 56 which imparts an additional 45 movementto the drawbar sections 17 and 25, as shown in FIG. 5, swinging theunits 10 up to their substantially vertical position. The arm 56 may belocked in this position by disposing the forward pin 78 in an additionalset of openings 84 (FIG. 6). The pins 78 in this position serve as apositive lock for holding the implement units in their elevatedposition. The cylinder 20 may now be slightly retracted to relievepressure on the pivot pins 59 and 73, the openings 81 being disposedrelative to the stop 79 so that there is a slight amount of lost motionavailable for the arm 72. The cylinder 20 may then be removed and theimplement units 10 held in the vertical position (FIG. 5) by the lock-uppin 78.

For road transport it is necessary to have the normally outwardlyextending drawbar sections 25 swung backwardly into a folded or trailingposition (FIG. 7) and in order to accomplish this easily and quickly weprovide an outer wheel mounting disclosed and claimed in our abovedescribed parent application, that makes it possible to shift the outergauge wheels from their working position (FIG. 1) into a positionaccommodating transport of the drawbars 25 in a trailing or foldedposition. The outer gauge wheels and their mounting means will now bedescribed.

FIG. 2 shows the right hand bar supporting an outrigger wheel in itsnormal working position, corresponding to the position shown in FIG. 1.Each of the outer or gauge wheels is indicated by the reference numeral90 and is shown as journaled on a stub axle means 91 bolted to an axlestandard bar 92. The forward or upper end of the bar, which is square incross section, is received in a laterally swingable axle bearing member94 carried by suitable mounting means 95 on the adjacent outer endportion of the associated bar 25. The member 94 includes a sleevesection 97 shaped to non-rotatably receive the wheel standard 92 but thelatter is slidably disposed within the sleeve section 97 and is held indifferent positions therein by means of a locking pin 98 that isinsertable in the openings in the upper portion of the sleeve section 97and a selected opening 99 in the standard 92. The axle bearing member 94is provided with a pair of apertured lugs 102 that are swingable on across pin 193 cartied in apertured lugs 194 formed on the support member95 that is adjustably fixed by U-bolts clamps 107 to the associated bar25.

The axle bearing member 94 and the wheel 90 and associated parts areheld in their normal working position (FIG. 1) in which the wheels 99*support the outer ends of the bars 25 for generally vertical movementrelative to the central carriage 11, by means of a U-shaped lockingmember 111 having one end 112 inserted in an opening in an apertured lug113 carried on the member 94, the other end 116 of the locking member111 being inserted in an inner set of openings 117 (FIG. 8) formed inapertured lug means 121 carried by or formed on the support member 95.

With the wheels 90 and associated parts locked in the position justdescribed, whenever the rockable bars 17 and 25 are rocked by extensionof the power unit 29, the implement units are raised and the wheels 99lowered, thereby raising the outer end portions of the outer bars 25. Byvirtue of the double operation of the power unit 20, described above,the bars 17, 25 can be rocked through substantially 90, it beingunderstood that the braces 28 are removed before this action takesplace. However, if the bars 17, 25 are to be rocked only through 45, itis not necessary to remove the braces 28 as will be clear from FIG. 3,since the outer end of the braces are pivotally connected at 32 with theassociated bars 25. Assuming, however, that the implement is to beraised into the position shown in FIG. 5 for transport, and the outerbars and associated implement units are to swing rearwardly into anarrowed position for transport, \as illustrated in FIG. 7, thefollowing operations are performed in substantially the order named.

First, the braces 28 are detached and laid on the car- Iiage frame 12and then the power unit is operated to swing the bars 17, throughapproximately 45, bringing the bars 25 and gauge wheels 90 substantiallyto the position shown in FIG. 3, in which the outer ends of the bar 25are raised by virtue of the downward movement of the gauge wheels 91)relative thereto. Stands are then placed under the outer ends of the bar25, one of such stands being indicated at S in- FIG. 4. After the standsare placed under the bars 25, the power unit 20 is operated to lower theimplement units 10, thus raising the wheels 91 upwardly and permittingthe outer ends of the bar 25 to be supported on the associated stands S.

The next operation to be performed is to take out the U-shaped lockingpin 111 and the pin 98, as shown in FIG. 2, after which each wheel maybe manually swung through approximately 90 over into the position shownin FIG. 4 parallel to the associated bar 25, it being understood thatthe bars 25 are supported on the stands S at this time. Swinging thewheel 90 over into the position shown in FIG. 4 brings the apertured endof the lug 113 in line with the apertures 117 in the lug means 121, andinsertion of the long end 116 of the locking pin 111 into theregistering openings serves to lock the bearing number 94 in its newposition (FIG. 4) with the wheel 99 occupying a position in a planeparallel to the associated bar 25. Also, the wheel standard 92 isshifted forwardly and the pin #98 inserted in the sleeve 94 and throughthe lower opening 99 (FIG. 2) in the wheel standard 92. Next, the powerunit 24 is operated to swing the bars 17, 25 through an'additional 45bringing the im plement supporting arms 41 substantially into a verticalposition, as illustrated in FIG. 5. This movement of the bars 25 swingsthe gauge wheels 90, now disposed parallel to the bars 25, into a lowerposition (FIG. 5) and since the wheels 99 are torward of the axis ofrocking of the bars 17, 25, the outer ends of the bar 25 are raised offthe stands S, whereupon the latter may be removed. The parts are nowarranged as shown in FIG. 5 from which it will be seen that driving theimplement forwardly will automatically cause the outer ends of the bar25- and associated parts to swing rearwardly toward one another tuitilthe wheels 99 are in a generally fore and aft extending position, asshown in MG. 7, the outer 'wheels 90 trailing behind the oarriage wheels15. If desired, suitable means rnay be provided for locking the rightand left hand bars 25 together in a trailing position (FIG. 7), butpreferably the wheels 90 are arranged to have a slight toe-in andtherefore under most conditions interconnecting means are not required.

When moving the outfit in trailing transport position (FIG. 7) it isdesirable to relieve the hydraulic system of all unnecessary loads, andto this end the locking pin 78 is disposed as shown in FIG. 5, holdingthe arm 56 in its forwardmost position which locks the center orcarriage drawbar 17 in the position shown in FIG. 5 land the bars 25 inthe positions shown in FIG. 7.

When it is desired to restore the implement to its operating orwidespread position it is preferable to shift the ground wheels or gaugewheels 90 from the positions shown in FIGS. 4, 5 and 7 into the positionshown in FIG. 8. This is done by first removing each locking pin 111from the associated openings 117 in the lug means 121, grasping theassociated gauge wheel 90* and shifting the same about a generallyvertical axis a small amount sufiicient to carry the apertured end ofthe lug 119 outwardly to a point alined with an outer set of openings125, and then inserting the end of the pin 111 in the laiined openings,as shown in FIG. 8, thus locking the wheels 99 in a rearwardly divergingposition. With the wheels 99 in this position, the output may then behacked and the wheels 99 will automatically cause the bars 25 to beswung laterally outwardly and around into a position alined laterallywith the center of carriage-supported bar 17. The stands may then bereinstalled nndereneath the outer ends of the arm 25, the cylinder orpower unit 20 operated, after the locking pin 78 (FIG. 5) have beenremoved, to rock the bars 25 around substantially into the positionshown in- FIG. 4, after which the wheels may be brought back to theposition shown in FIG. 2 by a substantial reverse of the operationsdescribed above. Then by rocking the bars 17, 25 downwardly, the outerends are againsupported on the wheels 99 and the stands may be removed.

While we have shown and described above the preferred structure in whichthe principles of this invention have been incorporated, it is to beunderstood that our invention is not to be limited to the particularmeans, shown and described above, but that, in fact, widely differentmeans may be employed in the practice of the broader aspects of ourinvention.

What we claim, therefore, and desire to secure by Letters Patent is:

1. In an agricultural implement having a part to be moved in two stagesbetween two positions, mechanism for moving said part from one positionto another, comprising a hydraulic ram unit, a pair of pivotally mountedarms on which said ram is carried, motion transmitting means connectingone of said arms with said part, a first stop means engageable with theother of said arms whereby extension of said ram unit acts to shift saidone arm and the associated part in one direction from one of theirpositions part way toward their other position, second stop means actingagainst said one arm to hold the latter against movement in the otherdirection away from said part way position, whereby retraction of saidram unit serves to shift said second arm toward said one arm into asecond position, third stop means acting against said second arm in itssecond position to hold it in that position, whereby a second extensionof said ram unit acts to shift said one arm and said associated part therest of the way into their said other position, and releasable meansengageable with said one arm to hold the latter in said other position.

2. A foldable drawbar for agricultural implements comprising a wheeledcarrier frame, a transversely disposed articulated drawbar memberrockably mounted on said carrier frame, said member including a centerbar supported on said frame and outer bars carried at their inner endson said center bar, lift arms on said center and outer bars and adaptedto be connected with implement units to raise the latter, said armsbeing swingable through a first extent to raise said units off theground and through a second extent to lift said implement units into aposition to accommodate folding of said outer bars and the implementunits carried on the lift arms associated therewith, and means connectedwith said center bar to rock the latter and said outer bars through saidfirst and second extents, said means comprising an extensible andretractable hydraulic ram unit, first and second arms swingably mountedon said carrier frame, means connecting said ram unit with said firstand second arms, a first stop means on said carrier frame located on thelatter so as to receive the reaction of said second arm when the latteris extended to shift said first arm and said center bar through saidfirst extent to partially raise said implement units, a second stopmeans carried by said carrier frame and disposable in a positionadjacent said first arm to hold the latter against movement out of theposition to which it is moved when the implements are partially raised,whereby retraction of said ram unit acts to shift said second arm awayfrom said first st-op means, a third stop means carried :by said carrierframe to engage said second arm and hold the latter in the position towhich it is moved away from said first stop means-by retraction of saidram unit, whereby a subsequent extension of said ram unit acts to shiftsaid first arm and said center bar through said second extent tocompletely raise said implement units.

3. The invention set forth in claim 2, further characterized by lock-upstop means carried by said carrier frame and disposable thereon to holdsaid first arm in the position it occupies when said implement units arecompletely raised, thus accommodating removal of said ram unit from saidfirst and second arm.

4. In an agricultural implement having a part to be moved in two stagesbetween two positions, mechanism for moving said part from one positionto another, comprising an extensible and retractable power means, a pairof pivotally mounted arms on which said power means is carried, motiontransmitting means connecting one of said arms with said part, a firststop means engageable with the other of said arms whereby extension ofsaid power means acts to shift said one arm and the associated part inone direction from one of their positions partway towards their otherposition, a second stop means disposable in a position adjacent said onearm to hold the latter against regressive movement out of the positionto which it is moved, whereby retraction of said power means acts toshifit said second arm away from said first stop means, a third stopmeans engagable with said other arm to hold the latter in the positionto which.

it is moved away from said first stop means by retraction of said powermeans, whereby a subsequent extension of said power means acts to shiftsaid first arm and said associated part the rest of the way into theirother position.

References Cited in the file of this patent UNITED STATES PATENTS

4. IN AN AGRICULTURAL IMPLEMENT HAVING A PART TO BE MOVED IN TWO STAGESBETWEEN TWO POSITIONS, MECHANISM FOR MOVING SAID PART FROM ONE POSITIONTO ANOTHER, COMPRISING AN EXTENSIBLE AND RETRACTABLE POWER MEANS, A PAIROF PIVOTALLY MOUNTED ARMS ON WHICH SAID POWER MEANS IS CARRIED, MOTIONTRANSMITTING MEANS CONNECTING ONE OF SAID ARMS WITH SAID PART, A FIRSTSTOP MEANS ENGAGEABLE WITH THE OTHER OF SAID ARMS WHEREBY EXTENSION OFSAID POWER MEANS ACTS TO SHIFT SAID ONE ARM AND THE ASSOCIATED PART INONE DIRECTION FROM ONE OF THEIR POSITIONS PARTWAY TOWARDS THEIR OTHERPOSITION, A SECOND STOP MEANS DISPOSABLE IN A POSITION ADJACENT SAID ONEARM TO HOLD THE LATTER AGAINST REGRESSIVE MOVEMENT OUT OF THE POSITIONTO WHICH IT IS MOVED, WHEREBY RETRACTION OF SAID POWER MEANS ACTS TOSHIFT SAID SECOND ARM AWAY FROM SAID FIRST STOP MEANS, A THIRD STOPMEANS ENGAGEABLE WITH SAID OTHER ARM TO HOLD THE LATTER IN THE POSITIONTO WHICH IT IS MOVED AWAY FROM SAID FIRST STOP MEANS BY RETRACTION OFSAID POWER MEANS, WHEREBY A SUBSEQUENT EXTENSION OF SAID POWER MEANS,ACTS TO SHIFT SAID FIRST ARM AND SAID ASSOCIATED PART THE REST OF THEWAY INTO THEIR OTHER POSITION.